System and method for forming a junction between elements of a modular endovascular prosthesis

ABSTRACT

The present invention provides a system and a method for forming in vivo a junction between a first and a second element of a modular endovascular prosthesis used for repairing defects in vessels and other lumens within the body of a patient. The first element is adapted to have a receiving element, and the second element is adapted to have a protruding element. In the final deployed configuration of the endovascular prosthesis, the protruding element of the second element is adapted to be engaged with the receiving element of the first element, substantially preventing axial separation of the elements relative to each other. The receiving element of the invention may have various forms, and may include a fold in the wall of the first element, an expandable framework having protruding struts, or a flexible thread. The protruding elements of the invention may be formed from an expandable framework having protruding struts, or may be formed from a fold in the wall of the second element, or may comprise a flexible thread.

BACKGROUND OF THE INVENTION

The present invention relates generally to intraluminal endovascularprostheses which are used for repairing defects in vessels and otherlumens within the body of a patient. More particularly, the presentinvention relates to systems and methods for forming, in vivo, a robustjunction between one element of a modular endovascular prosthesis whichhas been implanted in a patient, and another element.

Aneurysms are discrete dilations of the arterial wall. One of the mostcommon, and among the most life threatening, is an aneurysm of theabdominal aorta between the renal and iliac arteries. If untreated, theaneurysm dilates progressively with an ever increasing risk of ruptureand hemorrhagic death.

One method of treatment is provided by direct surgical intervention, inwhich the defective vessel may be bypassed or replaced using aprosthetic device such as a synthetic graft. The risks involved indirect surgical intervention of this magnitude are great, and include anextensive recovery period and a high morbidity rate.

In recent years a less invasive method of treatment has evolved througha series of inventions. The details vary, but, conventionally, aresilient tubular conduit fashioned from flexible material (hereinreferred to as a “graft”) is introduced into the defective vessel bymeans of catheters introduced into the femoral artery. The graft may beattached to the non-dilated arteries above and below the aneurysm usingexpanding metallic or plastic cylinders which may include barbs orhooks. The fluid pressure on the diseased arterial wall is reduced bythe barrier provided by the graft. The field of art has developed sinceits early stages and in certain circumstances the implantation of graftsin the patient in “modular” form is now possible and may be desirable. Amodular graft is one made up of different modular elements, each ofwhich is implanted in the patient at a different stage, the differentelements then being joined to each other by a suitable junction invivo—that is, after introduction into the patient's vascular system.

While modular grafts have the advantage of reducing problems such astwisting of the graft during deployment, their use and the necessaryformation in vivo of a junction between their elements is neverthelessattended by numerous complications. The most troubling long-termcomplication specific to the junction includes disruption of thejunction, which may be caused by dislocation of one element relative toanother through vascular movement or may be the long-term consequence ofdownstream fluid force. Once a junction between modular elements of anendovascular prosthesis has been disrupted, fluid leakage into theregion between the prosthesis and vascular wall will likely follow,thereby diminishing the efficacy of the prosthesis in reducing fluidpressure on the diseased vascular wall.

In the prior art, there are various kinds of junction formed in vivobetween tubular elements of a modular prosthesis. Conventionally, thejunctions used in the art may depend upon friction between theoverlapping elements to hold the elements in place relative to eachother. In other cases, the overlapping portion of one element may beadapted to form a frustoconical shape compatible with the overlappingportion of the other element. This serves to enhance the frictionalconnection between the elements and provides a degree of mechanicalconnection. However, each of these junctions may be disrupted by arelatively small force.

In the prior art of endovascular repair with a modular prosthesis, theretherefore exists a need to form in vivo a robust and secure junctionbetween modular elements which will not be dislocated by vascularmovement or downstream fluid flow. The present invention addresses needswhich are found in the prior art.

SUMMARY OF THE INVENTION

Briefly, and in general terms, the present invention provides a systemand a method for forming in vivo a junction between a first element anda second element of a modular endovascular prosthesis used for repairingdefects in vessels and other lumens within the body of a patient.

According to the present invention, the first element of such modularprosthesis is adapted to include a protrusion receiving element, and thesecond element is adapted to include at least one protruding element. Inthe final deployed configuration, the protruding element is adapted toengage the receiving element to thereby provide a robust and securejunction.

In a preferred embodiment, the receiving element may be defined bythread loops circumferentially configured about an interior wall of thefirst element and adapted to receive the protruding element of thesecond element. In a further embodiment, the receiving element may beformed from an inward fold in the inner surface of the distal end of thefirst element to thereby define an annular pocket for receiving thesecond element. In yet further embodiments, the receiving element mayembody an expandable framework having struts.

In a preferred embodiment, the second element is adapted to include atleast one protruding element such as the strut of a frame which isadapted to engage the receiving element of the first element. In furtherembodiments, the protruding element may be formed from an outward foldin the wall of the second prosthetic element to define an annularpocket, or formed from thread loops attached to a wall of the secondelement.

In a preferred method of deploying first and second elements, the firstelement is deployed at a desired position within the patient'svasculature. Thereafter, the second element is positioned, in compressedcondition, such that the protruding element of the second element islongitudinally clear of the receiving element. The second element isthen expanded, allowing the protruding element to engage the firstelement. The interaction of the protruding element with the receivingelement provides a barrier to axial separation of the two elementsrelative to each other.

It will be appreciated that, after implantation, longitudinal movementof the second element relative to the first element generally does notoccur where the junction between the first and second prostheticelements is arranged to benefit from forces associated with downstreamfluid flow. Moreover, any force promoting longitudinal movement of thesecond element will be resisted by the frictional connection between thefirst and second elements.

Other features and advantages of the present invention will becomeapparent from the following detailed description, taken in conjunctionwith the accompanying drawings, which illustrate, by way of example, theprinciples of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view, depicting a first component of a modularendovascular prosthesis;

FIG. 2 is a perspective view, depicting a second component attached tothe leg of the modular endovascular prosthesis shown in FIG. 1;

FIG. 3 is a schematic view, depicting a third component attached to themodular endovascular prosthesis shown in FIGS. 1 and 2.

FIG. 4 is a cross-sectional view, depicting a first preferred embodimentof a receiving element;

FIG. 5 is a cross-sectional view, depicting a variation of the receivingelement of FIG. 4;

FIG. 6 is a cross-sectional view, depicting a second embodiment of areceiving element;

FIG. 7 is a cross-sectional view, depicting a third embodiment of areceiving element;

FIG. 8 is a perspective view, depicting a first embodiment of aprotruding element;

FIG. 9 is a perspective view, depicting a second embodiment of aprotruding element;

FIG. 10 is a cross-sectional view, depicting a third embodiment of theprotruding element;

FIG. 11 is a perspective view, depicting a fourth embodiment of theprotruding element;

FIG. 12 is a perspective view, depicting a fifth embodiment of theprotruding element;

FIG. 13 is a partial cross-sectional view, depicting the delivery of asecond element in relation to a first element;

FIG. 14 is a partial cross-sectional view, depicting the second elementof FIG. 3 in an expanded condition;

FIG. 15 is a partial cross-sectional view, depicting an engagement ofthe second element of FIG. 14 with the first element;

FIG. 16 is a cross-sectional view, depicting an expandable annularelement incorporated into the embodiment shown in FIG. 6;

FIG. 17 is a partial cross-sectional view, depicting a fourth embodimentof the first element; and

FIG. 18 is a partial cross-sectional view, depicting an alternativeapplication of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In general, the system and method of the present invention for forming ajunction between first and second elements of a modular endovascularprosthesis is achieved by adapting the first element to include areceiving element, and by adapting the second element to include atleast one protruding element which is configured to engage the receivingelement and, thus, prevent axial separation of the first and secondelements relative to each other.

Referring to FIGS. 1–3, an exemplary modular endovascular prosthesisincorporating the present invention is described. It will be appreciatedby one of ordinary skill in the art that it is within the scope of thepresent invention to utilize the present junction at the joining of anytwo elements in other modular endovascular prosthesis as well forexample the prostheses described in U.S. Pat. No. 5,993,481 to Marcadeet al., U.S. Pat. No. 5,938,696 to Goicoechea et al., U.S. Pat. No.5,713,917 to Leonhardt et al., U.S. Pat. No. 5,575,817 to Martin, U.S.Pat. No. 5,824,040 to Con et al., U.S. Pat. No. 5,824,037 to Fogarty etal., U.S. Pat. No. 5,632,772 to Alcime et al. and published PatentCooperation Treaty WO 99/11199 to Kujawski et al. FIG. 1 shows a firstcomponent 20 of an endovascular prosthesis, configured to be used in therepair of a bifurcated corporeal vessel. The first component 20 has atrunk portion 21 and a pair of legs 22, 23. An expandable fixationdevice 24 may be connected to a superior end of the trunk 21 tofacilitate attachment of the first component to a vascular wall of atarget vessel. An expandable framework 25 may be used to maintain thepatency of a lumen of the prosthesis where necessary.

FIG. 2 depicts a manner in which a second prosthetic component 27 may beconnected to the inferior end of a leg 22 of the first component 20.FIG. 3 further exemplifies how a third prosthetic component 28 may beconnected to the inferior end of the other leg 23 of the first component20, which may be configured with a bell-bottom profile to assist thesurgeon in introducing a third component 28 into the lumen of that leg23. Further expandable frameworks 25′, 25″, 25′″ are shown maintainingthe patency of the lumens of the prosthesis, and may be attached toeither the internal or external wall of the prosthesis, as shown.Additionally, further tubular components (not shown) may be added toexposed ends of the second and third components 27, 28, until thedesired overall configuration is achieved, allowing fluid to flow fromthe first component 20 to the second 27 and third 28 components.

In modular systems such as the one shown in FIGS. 1–3, it is importantto ensure that there is no leaking at junctions between the variouscomponents of the modular systems. One manner of providing such ajunction is to configure one component at a junction with a receivingelement and the other with a protruding element that is sealinglyreceived in the receiving element.

The receiving element of the present invention may assume a number ofdifferent forms. One aspect of the receiving element of the presentinvention is exemplified in FIG. 4, which shows a portion of a firstprosthetic element 30 of a modular endovascular prosthesis, having aninferior end portion 42. A flexible thread 58 is circumferentiallyattached to the wall of the first prosthetic element 30 by means ofconnectors 59. The thread 58 is configured to have portions whichsuspend freely from the connectors 59, the same being adapted to receiveand to retain a protruding element attached to a second prostheticelement, as will be more fully described herein. The connectors 59 maybe simply stitched through the wall of the first prosthetic element 30.Both the thread 58 and the connectors 59 may be made from any flexiblesubstance which is durable and biocompatible. For example, Dacron™polyester suture material has been found to be suitable for forming thethread. In an alternative embodiment, the thread 58 may be routed in andout of the wall of the first prosthetic element 30, as exemplified inFIG. 5.

In a second embodiment of the receiving element of the present invention(FIG. 6), the inferior end-portion 42 of the first element 30 of themodular endovascular prosthesis, includes an annular pocket 44 formed byfolding the first element inwards. The resultant annular pocket 44includes a rim 45 and is secured in a fixed position by a plurality ofties 46, which may consist of threads, staples, stitches, rivets, wire,heat welding, or any suitable tying means. The assembly is therebyadapted to receive a protruding element connected to a second prostheticelement.

In a third embodiment (FIG. 7), the first prosthetic element 30 includesan expandable framework 50 attached to an interior wall of the firstprosthetic element 30 by means of connectors 59. As with the previousembodiment, such connectors can consist of threads, staples, stitches,rivets, wire, heat welding, or any suitable tying means. The framework50 has struts 54 which include tips 56 which are configured to protruderadially inward, thus providing an annular space suitable for receivinga protruding element attached to a second prosthetic element. The tips56 of the struts 54 may be rounded, to prevent injury to any material ofthe prosthesis with which they might come into contact.

The second prosthesis element of the present invention can assume anumber of different forms. Turning to FIG. 8, there is shown oneembodiment of a protruding element which is connected to a superiorend-portion 61 of a second prosthetic element 60 which is configured tobe joined to a first prosthetic element with a receiving element, suchas those shown in FIGS. 4–7. The protruding element 61 may be formed byconnecting an expandable framework 62 to the second prosthetic element60. The expandable framework 62 includes a plurality of struts 64 whichprotrude radially outwardly. In a preferred embodiment, the framework 62is attached to an outer wall of the second prosthetic element 60 by aplurality of connectors 59, which are of similar form and substance tothe connectors previously described. The tips 66 of the protrudingstruts 64 may be rounded, so as to minimize any trauma to any prosthesismaterial with which they come into contact. The protruding element 61 ofthis embodiment is formed by the outwardly protruding struts 64 of theframework 62, which are adapted to be seated within a receiving elementattached to a first prosthetic element.

FIG. 9 depicts a second embodiment of a protruding element of thepresent invention. In this aspect, the protruding element is defined byan expandable framework 72 having outwardly protruding struts 74 withblunt tips. The expandable framework 72 is adapted to be attached toinside walls of the second prosthetic element 60, allowing the struts toprotrude radially outward beyond the superior end 61 of the secondprosthetic element 60. The struts 72 may take a variety of forms, andmay have a simple curved hook shape.

It will be appreciated that the expandable framework 62, 72 and thestruts 64, 74 may have any shape which achieves the function ofproviding a protruding element suitable for engaging the receivingelement of a first prosthetic element 30. In a preferred aspect of theinvention, the framework 62, 72 may be self-expanding. However, inalternative embodiments a balloon-expanded framework may be used. Theframework 62, 72 may be formed of a corrosion resistant material whichhas good spring and fatigue characteristics. Materials found to beparticularly satisfactory are nickel-titanium alloys such as Nitinol,and chromium-cobalt-nickel alloys such as Elgiloy™.

With reference to FIG. 10, a third embodiment of the protruding elementof the present invention is described for connecting with a receivingelement as described. In this embodiment, the wall of the secondprosthetic element 60 is folded radially outwardly, to form an externalannular pocket 85. The folded pocket 85 may be secured in a fixedposition in relation to the second prosthetic element by means of tiesor connectors 46, such as have been previously described herein.Additionally, as shown in FIG. 11, the protruding element may be formedfrom a thread 88, circumferentially attached to the outer wall of thesecond prosthetic element 60. Attachment of the thread to this secondelement 60 may be achieved by connectors 89, or otherwise by routing thethread 88 in and out of the wall of the second prosthetic element, asexemplified in FIG. 12. It will be appreciated that, where theprotruding element exemplified in FIGS. 10–12 is employed, the inferiorend portion 61 of the second prosthetic element 60 may be expanded froma compressed condition to an expanded condition by using an expandableframework (not shown) similar to the expandable framework 62 describedabove, the same being placed on an interior wall of the secondprosthetic element 60.

Turning now to FIGS. 13–15, a preferred method of joining first andsecond prosthetic elements of a modular endovascular prosthesisincorporating the present invention in the vasculature of a patient isdescribed. FIGS. 13–15 depict the first prosthetic element withreceiving element exemplified in FIG. 6 in combination with the secondprosthetic element with receiving element exemplified in FIG. 8, but anysuitable combination of receiving and protruding elements may be usedaccording to the principles disclosed. A first prosthetic element 30with receiving element 44 is initially deployed within the vascularsystem (not shown) of the patient. Methods of deploying flexibleendovascular prosthetic elements within the vasculature of a patient areknown in the art, in which deployment is conventionally achieved byplacing the prosthetic element in a first compressed condition in adelivery sheath/capsule for insertion into the vascular system viadelivery catheters. In general, once the first element 30 reaches thedesired position within the vascular system, it is released from adelivery sheath/capsule, whereupon it is expanded from a compressedcondition to an expanded condition, and may be attached to the wall ofthe vascular lumen using balloon-expanded or self-expanding attachmentsystems (not shown).

Once the first prosthetic element 30 has been deployed to assume itsexpanded condition, the superior end 61 of the second prosthetic element60 configured with framework 62 in a compressed condition, is insertedinto the lumen of the first prosthetic element 30 at the inferior end 42thereof (FIG. 13). In the preferred method, the second prostheticelement 60 and framework 62 are disposed in a compressed condition overa delivery catheter 90 and confined within a jacket/sheath 94. Thedelivery catheter 90 with jacket 94 assembly may be inserted into thevascular system over a guidewire 98 configured to extend from the pointof access (not shown) into the vasculature and through the interior ofthe first prosthetic element 30. When the entire framework 62 of thesecond element 60 is advanced beyond the receiving element of the firstprosthetic element 30 (an annular pocket 44 in the case exemplified, butthe principle applies to all embodiments of the receiving element), thesecond prosthetic element 60 and attached framework 62 are deployed bywithdrawing the jacket 94, thereby permitting the framework 62 to assumean expanded condition (FIG. 14).

Accurate positioning of the second prosthetic element 60 relative to thefirst 30 may be achieved by using radiopaque markers, attached to thewalls of both first and second prosthetic elements 30, 60, inconjunction fluoroscopy, for example. Use of radiopaque systems forpositioning intraluminal devices is well known in the art and is notdescribed here. It is to be further appreciated that additionalexpanding frameworks (not shown) may be used in conjunction with thefirst prosthetic element 30 in order to hold open the first element 30at its inferior end 42, so that the superior end 61 of the secondprosthetic element 60 may be introduced therein.

Once the second prosthetic element 60 with attached framework 62 isdeployed and expanded (FIG. 14), the protruding struts 64 press againstthe interior wall of the first prosthetic element 30. The secondprosthetic element 60 is then either moved longitudinally so that theprotruding struts 64 of the framework 62 become seated in the receivingelement 44 of the first prosthetic element 30, or it may be left inposition and allowed to migrate thereto under the force of downstreamfluid flow, so that it is eventually positioned with the protrudingstruts 64 seated in the receiving element 44 (FIG. 15). It is to beappreciated that, once the protruding struts 64 of the framework 62 areso seated, a robust mechanical barrier to distal migration of the secondprosthetic element 60 relative to the first prosthetic element 30 isprovided. Such a mechanical barrier has the advantage of being aneffective barrier to axial separation of the first prosthetic element 30from the second prosthetic element 60. Significantly, the overlapbetween the material of the first and the second prosthetic elements 30,60 provides a fluid seal substantially preventing leakage of fluidthrough the junction to the region between the endovascular prosthesisand the vascular wall.

In a further aspect of the invention (FIG. 16), the receiving element 44exemplified in FIG. 6 may be further equipped with an expandable annularelement 100 that is inserted into the pocket 44. This arrangementfacilitates holding the distal end 42 of the first prosthetic element 30open, in order to aid the introduction of the second prosthetic element60 therethrough. The annular element 100 is expandable between a firstcompressed condition and a second expanded condition. The annularelement 100 may be compressed during delivery to expand upon deploymentfrom a delivery catheter, and, like the self-expanding embodiment of theframework 62, may be made from a corrosion resistant material which hasgood spring and fatigue characteristics.

In yet a further aspect of the invention (FIG. 17), a first prostheticelement 130 includes an annular receiving element 132 formed in theinternal walls of the first element 130 medial superior 133 and inferior134 ends thereof. The receiving element 130 is formed by folding anannular section of the first element 130 upon itself and tacking thefolds with connectors 46. This arrangement has the advantage ofproviding an added area of contact 135 between the material of the firstand the second prosthetic elements 130, 60 which enhances the efficacyof the fluid seal between the elements. The first prosthetic element 130may be held open at its inferior end by an expandable framework (notshown) of similar configuration to the expandable framework 62 describedin the present invention. In a variation of this aspect, as exemplifiedin FIG. 18, the area of overlap 135 may be configured to have abell-bottom profile, to facilitate guiding and inserting the secondprosthetic element 60 into of the first prosthetic element 30. Thebell-bottom profile may be held in position by an expandable framework140, a similar arrangement which is shown in FIG. 1.

It will be apparent from the foregoing that, while particular forms ofthe invention have been illustrated and described, various modificationscan be made without departing from the spirit and scope of theinvention. Accordingly, it is not intended that the invention belimited, except as by the appended claims.

1. A modular endovascular prosthesis, comprising: a first element havinga cylindrical interior wall surface, an inferior end and a superior endand having a receiving element formed on the cylindrical interior wallsurface of said first element, the receiving element having a receivingportion that suspends freely from the wall and can be translated bothlongitudinally or transversely with respect to the first element; and asecond element having an inferior end and a superior end and furtherhaving at least one protrusion extending therefrom, said protrusionconfigured to be received within the receiving portion of said receivingelement.
 2. The prosthesis of claim 1, wherein said receiving element isdefined by thread loops.
 3. The prosthesis of claim 2, said receivingelement further comprises connectors, said connectors attaching saidthread loops to said first element.
 4. The prosthesis of claim 2,wherein said thread loops engage said first element.
 5. The prosthesisof claim 1, wherein said protruding element is an expandable frameworkhaving protruding struts.
 6. The prosthesis of claim 5, wherein saidsecond element comprises a wall defining a lumen having an inner andouter surface, and said expandable framework is configured on said innersurface.
 7. The prosthesis of claim 5, wherein said expandable frameworkis self-expanding.
 8. The prosthesis of claim 5, wherein said expandableframework is balloon-expanded.
 9. A method for creating a junctionbetween a first element and a second element of a modular endovascularprosthesis wherein both first and second elements define a lumen,comprising the steps: configuring the first element with a receivingelement, the first element including a cylindrical interior wall surfaceand the receiving element having a receiving portion that suspendsfreely from the cylindrical interior wall surface of the first elementand can be translated both longitudinally or transversely with respectto the first element; configuring the second element with a protrudingelement; deploying the first element; moving a portion of the secondelement into the lumen of the first element; and deploying the secondelement so that the protruding element is received within the receivingportion of the receiving element.
 10. The method of claim 9, said stepof deploying the first element further comprises permitting the firstelement to self-expand.
 11. The method of claim 9, said step ofdeploying the second element further comprises permitting the secondelement to self-expand.
 12. The method of claim 9, said step ofconfiguring the first element with a receiving element furthercomprises: providing an expandable framework having protruding struts;and connecting the framework to the first element.
 13. The method ofclaim 9, wherein said step of configuring the first element with areceiving element further comprises: providing a thread; and connectingthe thread circumferentially to the first element.